Thermosensitive relay



June 7, 1927.

L. E. SPRAY THERMosENs1T1vE RELAY Filed Sept. 26, 1922 /N VENTO/f? I ma ci' @PM aqui-wlw@ Patented June 7, 1927.

UNITED STATE-s.

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THERHOSENSITIVE RELAY;

Application tiled September 26, 1922. Serial o. 590,726.

My invention relates to thermo-sensitive relays, that is, relays which depend for their action upon changes in the electrical characteristics of ya substance in response to Vti changes in temperature. One feature of my invention is the provision of a relay of this character adapted to control a plurality of A secondary circuits.

I will describe three forms of relays ernbodying my invention, and will then point out the novel features thereof in a claim.

In the accompanying drawin Fig. l is a view showing in vertical longitudinal section one form of thermo-sensitive relay einbodying my invention. Fig. 2 is a view showing in vertical longitudinal section a modified form of relay also embodying my invention. Fig. 3 is a view showing in verticalsection still another form of relay embodying my invention.

Similar reference characters refer to similar parts in each of the three views.

Referrin first to Fig. l, the reference characterV desi ates va heating element comprising a con uctor of suitable material such as nichrome. This heating element is provided with a primary circuit including a source of energy such as a battery B, and a switch S. 4Surrounding this heating element A is a layer or coating of insulating material D such as porcelain or glass. Supported on this insulating material D are a plurality of secondary umts K each comprising a cylindrical element C of thermosensitive substance having either a positive or a negative temperature coeflicient such for example, as copper oxide. A. contact band E of some electro-conducting material, such as copper, is placed about one end of each thermo-sensitive element C in contact therewith and serves as a terminal for connection to an external circuit. Surroundingv the other end of each thermo-sensitive element C and aced from the band E is another similarsband G. Each secondary unit K is provided with a secondary circuit which passes from the left hand terminal of a battery H, through band E, the associated thermo-sensitive element C, band Gr, 5 and an electro-responsive device J which as here shownis an electric lamp to the right hand terminal of the battery H.

The operation of the relay is as follows: I will assume that the substance C has a negative temperature coeiiicient. With the switch S open, the resistance of each element C is so great that it does not allow enough current to ass to light the associated lamp J. When t e switch S is closed, the battery B supplies current to the heating element producing heat which is transmitted through the insulating material D to the thermo-sensitive elements C. The increased temperature of each of these elements causes its resistance to be decreased and the current Which then passes through it andthe associated lamp J- from the battery H is enough to light the lamp which remains lighted as long as the element C remains hot. Vhen the switch S is opened, temperature of the relay decreases and the resistance of each of the thermo-sensitive elements increases causing a corresponding decrease in the current sup lied to the lamps J which then become extinguished.

In Fig. 2, which shows a modification of the relay described above, the insulating material is made in the form of a cylinder D in which a plurality of secondary units K are imbedded. Each of these units, thus insulated from the others, comprises a cylindrical element C of thermo-sensitive substance,.a contact rod imbedded in the center of this element and protruding from the relay either at the end or on the side so as to offer a terminal for connection to a secondary circuit, and acontact band G surrounding a portion of the element C` and having an outstanding lug G which protrudes through the insulating material D. Wound on the outside of the insulating cylinder D is a heating element A comprising a coil of wire provided with a primary circuit including a battery B and a switch S. Each secondary unit is provided with a circuit which passes from the left hand terminal of a battery I-I through contact rod E, thermo-sensitive element C, contact band G, a lamp J back to the right hand terminal of the battery H. The relay operates in precisely the same manner as the one shown in Fig. l. i

Fig. 3 shows another modication of the relay. A heating element A is wound in a coil upon a tube D of insulating material, and then a coating D of insulating material is placed on the coil, making a rigid tube of insulation having the heating element imbedded therein. Mounted on this tube are a plurality of secondar units K each comprising a contact band directly surrounding the insulatin tube, an annular element C of thermo-sensitive substance surrounding band E, and another contact band G surroundinlthe thermo-sensitive element C. A battery and a lamp J are connected in series with the two contact bands E and G, thus com leting, with the thermo-sensitive element the secondary circuit. A battery B, controlled by a switch S, supplies current to the heatin element A. When the switch is closed the attery B energizes the heating element A, producing heat which is transmitted through the insulating material D and D and the bands E to the thermo-sensitive elements C. The resultin decrease in the resistance of each element causes each lamp J to become lighted. When the switch S is opened, the temperature of the relay decreases and the lamps J vbecome extinguished as in Fig. 1.

In each form of relay shown herein the arts are so proportioned that the relation tween the applied voltages and the teinperature of each thermo-sensitive element is such that the changes in the conductivity of the therm0sensitive element are due almost entirely to changes in the temperature of the heating element A and are sensibly independent of temperature variations due to the secondary current carried by the thermosensitive element, so that under no circumstances can the heated condition of the thermo-sensitive element be maintained by the secondary current. That is to say the proportioning is such that the secondary current can have relatively little e'ect in determining the temperature and so the conductivity of the thermo-sensitive element. In so far as dimensions enter into the matter, each thermo-sensitive element referably has a comparatively short path ofcomparatively large area.

Although I have herein shown and described only three forms of relays embodying my invention, it is understood that various changes and modifications may be made therein within the scope of the appended claim Without departing from the spirit and scope of m invention.

Having thus escribed my invention, what I claim 1s:

A thermo-sensitive relay com rising n secondar unit made up of a cylin rical element o thermo-sensitive substance and spaced Contact bands surrounding said thermo-sensitive element and a primary element made up of a rod o electro-conductin material and a coating of electro-ins ating material deposited thereon, said primary ele ment being inserted in a hole in said secondar element.

n testimony whereof I aflix my s ture.

LESTER E. SP Y. 

